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Cryopreservation of Large Biological Systems

G.M. Fahy*

Naval Medical Research Institute

This is an abstract for a talk to be given at the Fifth Foresight Conference on Molecular Nanotechnology.

Large biological systems represent a challenge to cryobiologists because of their diverse cell populations, the inability to apply high cooling and warming rates, and the requirement for preservation not only of cells but also of extracellular connective tissue and cell-matrix and cell-cell connections. Examples of complex biological systems that tolerate massive distortion by ice exist, and even some mammalian organs have survived and functioned after extensive ice formation, but the general experience and concensus is that the best option for the cryopreservation of large systems is generally metastable or quasi-stable vitrification as introduced by Fahy in the early 1980's. With increasing size, vitrification becomes increasingly difficult on statistical grounds, but the volume fraction of the sample that undergoes injury from random heterogeneous nucleation may be small. Both the problem of rare nucleation events during cooling and the problem of devitrification on warming can be approached by the design of solutions that maximize biological viability but minimize ice crystal nucleation and ice crystal growth. Molecular design techniques can play a role in addressing these issues. As of this writing, it is probably possible to vitrify rabbit kidneys with preservation of viability in the vitrified state, but we do not yet have the technology to restore these kidneys to active function. However, in the future, it should be possible to warm these kidneys sufficiently quickly to demonstrate viability.

*Corresponding Address:
Gregory M. Fahy, Ph.D., Organ, Inc., c/o Naval Medical Research Institute, Building 29, Bethesda, MD 20889, email: 72124.1173@CompuServe.COM
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